The Naegleria fowleri amoeba got into St. John the Baptist Parish’s Water District No. 1, which provides water for about 12,500 residents.

CDC officials say ingesting water containing the amoeba is harmless because it cannot infect a person through the digestive system, but the contaminated water can prove fatal if it comes into contact with nasal passages, which is how it travels to the brain.

A four-year-old Mississippi boy contracted the amoeba while visiting St. Bernard Parish last year and later died.

“St. John is now under an emergency order to perform a 60-day free chlorine burn on the water system, in which the water lines are infused with free chlorine. That is a stronger, faster-acting disinfectant than the normal infusion of chloramines, a combination of chlorine and ammonia,” Littice Bacon-Blood reported for the New Orleans Times-Picayune. As a precautionary measure, the St. John school system closed off all the water coolers in its schools.